Indirect adaptive control of droplet dispensing in digital microfluidic systems

Digital microfluidics systems require advanced controllers to operate accurately since their parameters are subjected to change in environment and over time. Due to imperfect manufacturing processes, their fabricated system parameters may become different from the destined values. Hence, estimation based controllers are required to identify the system parameters. The electrowetting on dielectric can be precisely controlled to dispense desirable and repeatable droplets. However, the system parameters and their variation over time makes the control system challenging. This paper describes the application of an indirect adaptive trajectory controller for digital Pico-Droplet dispensing system. Forgetting factor recursive least square estimator is used to estimate the system parameters including capacitance and resistance of the occupying droplet between electrodes. Indirect adaptive technique is used to measure and control the droplet volume on the dispensing electrodes. Simulations of the estimator, tracking performance of dispensed droplet volume and the controller´s control effort are provided to demonstrate an accurate and high performance control approach.